public class NewJFrame extends javax.swing.JFrame {

public NewJFrame() {
initComponents();
jComboBox1.setEnabled(false);
jRadioButton1.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
jComboBox1.setEnabled(jRadioButton1.isSelected());
}
});
}

@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {

jRadioButton1 = new javax.swing.JRadioButton("Radio Button");
jComboBox1 = new javax.swing.JComboBox<>();

setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

jComboBox1.setModel(new javax.swing.DefaultComboBoxModel<>(new String[]{"Item 1", "Item 2", "Item 3", "Item 4"}));

javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jRadioButton1, javax.swing.GroupLayout.Alignment.TRAILING)
.addComponent(jComboBox1, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.PREFERRED_SIZE, 153, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(18, 18, 18))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addComponent(jRadioButton1)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);

pack();
}// </editor-fold>
/**
@param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
new NewJFrame().setVisible(true);
}
});
}

// Variables declaration - do not modify
private javax.swing.JComboBox<String> jComboBox1;
private javax.swing.JRadioButton jRadioButton1;
// End of variables declaration
}